The present invention relates to a buckle used in a safety belt device, such as a seat belt device for a seat of an automobile and, more particularly, to a buckle having a buckle switch which is switched by an engagement between a tongue and the buckle.
Currently, in various vehicles including automobiles, seat belt devices for protecting occupants in emergency, such as collision, are installed on seats thereof. In order to facilitate the occupant to wear on and off such a seat belt, a buckle is normally provided. In general, the buckle comprises a latch member which engages a tongue, wherein the latch member is biased by a spring in such a direction as to engage the tongue, and a locking member holding the latch member in the latched state where the tongue is engaged with the buckle.
By the way, the buckle is provided with a buckle switch for detecting the latched state in order to indicate the latched state where the tongue is engaged with the buckle, and to control the operation of other devices of the seat belt device, such as a retractor, and other devices installed in the vehicle, which should be operated depending on the operation of the seat belt device according to the latched state where the tongue is engaged with the buckle.
Conventional buckle switches generally used are contact type switches, such as a substrate type switch and a micro switch. In a buckle switch of this type, however, since switching actions are repeated at contacts of the buckle switch every time the tongue is engaged with and disengaged from the buckle, there is a possibility of contact failure due to abrasion of the contacts. This means that the durability of the buckle switch is not so well.
Thus, a buckle switch employing a switch with a non-contact type was proposed in Japanese Unexamined Patent Publication (KOKAI) H10-155521. The buckle switch of the non-contact type disclosed in this publication comprises a catoptric device having a field supply device and a field effect device, wherein the field supply device emits light to a reflecting surface of a latch member which locks the tongue and the field effect device senses reflected light reflected by the reflecting surface, thereby detecting the latched state or unlatched state of the tongue and the buckle.
Since the buckle switch of the non-contact type has no contact, there is no possibility of contact failure due to abrasion of the contacts. This means that the buckle switch has improved durability.
However, the buckle switch of the non-contact type which employs the catoptric device is easily affected by installation error between the latch member and the catoptric device, liquid, such as water and juice, foreign materials, such as dusts, and rust due to liquid. Therefore, there is a possibility that, in the affected condition, the catoptric device does not easily receive reflected light, so that the buckle switch does not securely operate. It should be noted that the buckle switch of the contact type is also easily affected by liquid, such as water and juice, foreign materials, such as dusts, and rust due to liquid.
The present invention has been made for solving the aforementioned problems, and an object of the present invention is to provide a buckle provided with a buckle switch which has improved durability and still can be securely operated.
To solve the aforementioned problems, the buckle according to the first aspect of the invention comprises at least, a base having side walls; an ejector which is disposed on the base movably in the longitudinal direction and moves according to an insertion of a tongue, the ejector allowing the tongue to come off the buckle when the engagement between the tongue and the buckle is released; a latch member which is pivotally supported by the side walls so as to pivot between its unlatched position and its latched position, is biased toward the latched position, and when the tongue is inserted into a predetermined position, pivots to its latched position where the tongue is engaged; an operating member for releasing the engagement between the tongue and the latch member which are in a latched state; and a lock member which is disposed between the side walls so as to move between its unlocked position and its locked position, is set in the locked position where the latch member is held in the latched position when the tongue is engaged with the latch member, and is moved to the unlocked position by the operating member where the engagement of the tongue by the latch member can be cancelled. The buckle further includes a buckle switch of a non-contact type which can be switched by detecting a movement of either one of the ejector, the latch member, and the lock member. The buckle switch comprises a magnet and a Hall element generating electromotive force by the magnetic field of the magnet. One of the magnet and the Hall element is attached to a fixed member, and the other of the magnet and the Hall element is attached to either one of the ejector, the latch member, and the lock member.
In the second aspect of the invention, the magnet comprises two magnet members having different directions of magnetic field. One of the two magnet members confronts the Hall element in the unlatched state where the tongue is not engaged with the buckle, and the other one of the two magnet members confronts the Hall element in the latched state where the tongue is engaged with the buckle.
In the third aspect of the invention, the buckle switch comprises a switch casing attached to the base, and a latch detecting movable member which is disposed on the switch casing so as to move following the movement of either one of the latch member and the lock member. One of the magnet and the Hall element is attached to one of the latch detecting movable member and the switch casing, and the other one of the magnet and the Hall element is attached to the other of the latch detecting movable member and the switch casing.
In the fourth aspect of the invention, the buckle switch further comprises biasing means disposed in the switch casinq for biasing the latch detecting movable member toward the outside of the switch casing when the buckle is shifted from the unlatched state to the latched state.
In the buckle of the present invention structured as described above, the buckle switch is switched in a non-contact manner by Hall effect by using the magnet and the Hall element. Therefore, there is no possibility of contact failure due to abrasion of contacts, thus significantly improving the durability as compared to switches of a contact type, such as a substrate type switch and a micro switch.
In addition, as compared to the buckle switch composed of a catoptric device disclosed in the aforementioned publication, the buckle switch of the present invention is not easily affected by installation error, liquid, such as water and juice, foreign materials, such as dusts, and rust due to liquid. The buckle switch of the present invention can be further securely operated.
Particularly, according to the fourth aspect, the biasing means biases the latch detecting movable member to securely slide in the projecting direction when the buckle is shifted from the unlatched state to the latched state, thereby stabilizing and securing the detecting operation of the buckle switch.